Projection exposure device and projection exposure method

Abstract

A projection exposure apparatus includes a mask mark illumination light source irradiating a mask mark with exposure light itself or a first alignment light having substantially the same wavelength as the exposure light, and an alignment unit having a work mark illumination light source irradiating a work mark with second alignment light having a wavelength different from the wavelength of the exposure light, an imaging device, and an imaging optical system. The imaging optical system includes a first dichroic prism for synthesizing the first alignment light and the light from the work mark and emitting the synthesized light toward the imaging device, and an optical path length changing optical system for splitting and merging the first alignment light, in which the optical positional relationships of the work mark and the image of the mask mark with respect to the imaging device are equivalent.

The invention claimed is: 
     
         1 . A projection exposure apparatus for irradiating a mask with exposure light, projecting a pattern formed on the mask onto a work by a projection lens, and exposing the work to the pattern, the projection exposure apparatus comprising:
 a mask mark illumination light source capable of irradiating an alignment mark of the mask with the exposure light itself or first alignment light having substantially the same wavelength as the exposure light; and   an alignment unit including:   a work mark illumination light source capable of irradiating an alignment mark of the work with second alignment light having a wavelength different from the wavelength of the exposure light;   an imaging device that obtains an image of the alignment mark of the mask by the first alignment light and the alignment mark of the work; and an imaging optical system including a synthesizing optical element emitting, toward the imaging device, a synthesized light obtained by synthesizing the first alignment light emitted from the mask mark illumination light source through the mask and the projection lens and a light from the alignment mark of the work, the imaging optical system allowing the imaging device to obtain the image of the alignment mark of the mask and the alignment mark of the work as an image, wherein:   the imaging optical system has an optical path length changing optical system for splitting and merging the first alignment light from the first alignment light and the light from the alignment mark of the work synthesized by the synthesizing optical element such that an optical path length of the first alignment light from the synthesizing optical element to the imaging device is longer than an optical path length of the light from the alignment mark of the work from the synthesizing optical element to the imaging device;   the image of the alignment mark of the mask obtained by the imaging device is formed on the optical path of the optical path length changing optical system; and   optical positional relationships of the alignment mark of the work and the image of the alignment mark of the mask with respect to the imaging device are equivalent.   
     
     
         2 . The projection exposure apparatus according to  claim 1 , wherein:
 the synthesizing optical element is a first dichroic prism having a pair of prisms whose adjoining surfaces inclined at 45° with respect to an optical axis of the first alignment light emitted from the projection lens forms a half mirror surface; and   in the prism facing the work, a surface orthogonal to the optical axis of the first alignment light forms a dichroic surface that reflects the first alignment light and transmits the second alignment light.   
     
     
         3 . The projection exposure apparatus according to  claim 1 , wherein:
 the optical path length changing optical system includes: a second dichroic prism including a plurality of prisms whose two adjoining surfaces respectively inclined at 45° with respect to the optical axis of the synthesized light emitted from the synthesizing optical element and forming dichroic surfaces reflecting the first alignment light and transmitting the second alignment light are orthogonal to each other; and   a pair of reflective optical elements respectively provided at positions away from the optical axis of the synthesized light emitted from the synthesizing optical element and having reflective surfaces orthogonal to each other such that the first alignment light reflected by one adjoining surface of the second dichroic prism enters the other adjoining surface of the second dichroic prism.   
     
     
         4 . The projection exposure apparatus according to  claim 3 , wherein:
 the alignment unit is provided to be horizontally movable back and forth between the projection lens and the work; and   the work mark illumination light source and the pair of reflective optical elements are disposed on a horizontal plane including the optical axis of the synthesized light emitted from the synthesizing optical element.   
     
     
         5 . A projection exposure method including the projection exposure apparatus according to  claim 1 , the method comprising:
 aligning the mask and the work based on the image of the alignment mark of the mask obtained by the imaging device and the alignment mark of the work; and
 irradiating the mask with exposure light, projecting the pattern formed on the mask onto the work by the projection lens, and exposing the work to the pattern.